It is proposed to investigate the feasibility of an immunochemically sensitive field effect transistor. We have shown that devices with polymeric membranes which have modified surface respond to the addition of proteins and other surface active components. There is a discernible difference between immunochemically active serum (antiserum) and a control serum in response of IMFET with immobilized antibody. This response is due, however, to the change of mixed potential which makes this device very nonspecific. Research will be focused on IMFETs with modified polarized solution/transistor interferences.